Polyhydric alcohols are used in food compositions to retain the original quality of the food on ageing and shipping or to obtain a texture or product quality that was not present in the original product. Sorbitol, glycerol, mannitol and other polyols are already used on a large scale as food additives.
Erythritol, a naturally occurring polyol sweetener, has relatively recently become available in significant amounts. Erythritol is used for its capacity to replace sugar while preserving the sweet taste. Erythritol is 60% as sweet as sucrose at the normal use level and is sweeter than mannitol and sorbitol. It is also used because it is excreted unmetabolised and therefore leads to an important calorie reduction.
Apart from the calorie reduction erythritol can also provide the texture of a `fatty mouthfeel`. Because of this characteristic erythritol is also suitably used as a fat replacer.
Since erythritol is not metabolised it will have little or no effect upon the normal body function. It may therefore be used in foodstuffs designed for people whose metabolizable carbohydrate intake must be restricted due to diabetes or obesity.
Erythritol is also used in sugarless chewing-gum applications. It is known that erythritol is not fermented by bacteria appearing in the mouth flora, and especially by Streptococci, therefore erythritol does not give rise to acidification. This acidification is one of the causing agents of caries. The Streptococci are also responsible for the formation of water-insoluble glucan which in turn forms the dental plaque. The dental plaque will retain microorganisms and therefore also stimulates caries formation. Products which contain erythritol instead of other sweetening agents have been tested in the so-called Muhlemann test (Imfeld, Th. and Muhlemann, H. R. J, Prev. Dentistry 4 8-14 (1977) and Imfeldt, Th. and Duhamel, L. Revue d'Odonto-stomatologie 9: 27-38 (1980)). This test is based on the intra-oral measurement of plaque pH. In this test a criterium for the indication `safe for teeth` is developed. A product or composition is called `safe for teeth` if the pH in the mouth does not drop below 6 after consumption of the product or composition. According to this criterium erythritol is considered as `safe for teeth`. Replacement of sugar by erythritol therefore reduces the amount of caries to a considerable degree.
All this is known for some time as evidenced by the vast amount of literature covering an ever growing field of potential applications for polyols in general and for erythritol in particular.
Erythritol is commercially produced by fermentation of glucose. Potential fermentation processes are described in European patents EP 0 136 802, EP 0 136 803, EP 0 136 804, EP 0 136 805, EP 0 262 463, EP 0 327 016 and EP 0 327 342. Chemical methods for the production of erythritol are well known and include hydrogenolysis of dialdehyde starch, reduction of formaldehyde and hydrogenolysis of sorbitol.
Erythritol, which is extensively marketed in Japan, is increasingly used as a sugar replacer in such applications as chocolates, candies, pie fillings, soft drinks etc. European patent application EP 0 009 325 describes the use of erythritol in the form of a sugarless cariostatic composition comprising at least 5% erythritol. The preferred use of this composition is in toothpaste or chewing gum and it is reported that preferably the sugars are completely replaced with erythritol. Moreover all examples relate to the total replacement of sugar.
European patent EP 0 511 761 describes instant pie fillings containing erythritol and sorbitol.
European patent EP 0 530 995 describes the application of erythritol or maltitol for the preparation of low cariogenic and low calorie lozenges.
European patent application EP 0 727 146, which was not pre-published, discloses a chocolate composition containing erythritol and an amount of maltitol sufficient to mask the cooling effect of erythritol. The chocolate preparations contain no sugar and the application only describes bitter (black) chocolate i.e. chocolate containing no milk powder or lactose.
Among the references relating to the non-cariogenic effect of erythritol the following are specifically pointed out. Kawanabe et al. Caries Res. 26 358-362 (1992) describes the non-cariogenecity of erythritol as a substrate. After studies in which rats were fed diets containing erythritol, sucrose or starch it was concluded that erythritol was not utilized as a substrate for tooth plaque formation. Furthermore, Streptococci did not produce lactic acid.
European patent application EP 0 561 089 describes the use of different combinations of hydrogenated mono-saccharides with polysaccharides. No specific mention is made of any special effects observed with erythritol let alone an anti-cariogenic effect of erythritol. Furthermore erythritol is not used in any of the experiments.
U.S. Pat. No. 4,518,581 describes the low- or anti-cariogenic properties of isomalto-oligosaccarides. In Table 1 it is demonstrated that erythritol, in an amount of 10% with respect to sucrose, does not inhibit the water-insoluble glucan formation by Streptococcus mutans 6715. Erythritol is therefore not classified as anti-cariogenic according to the criteria developed in this U.S. patent.
One of the major drawbacks of the use of erythritol as a sugar replacer is that it is much more expensive than some of the substances which it replaces. It would therefore be interesting to replace only a part of the sugar by erythritol while at the same time preserving the characteristics of erythritol specifically its non-cariogenic effect.